The present application claims priority to Japanese Application No. P11-029258 filed Feb. 5, 1999 which application is incorporated herein by reference to the extent permitted by law.
1. Field of the Invention
The invention relates to an optical waveguide device including an optical waveguide capable of propagating a light, an optical transmitting and receiving device, a method of manufacturing an optical waveguide device and a method of manufacturing an optical transmitting and receiving device.
2. Description of the Related Art
In the field of an integrated circuit (IC), a large scale integration (LSI) or the like, the technological advance improves an operating speed and a scale of integration, thereby rapidly promoting an enhancement in performance of a microprocessor and an increase in a capacity of a memory chip. However, the increase in a transmission rate of an electric signal and the increase in density of signal wiring are bottlenecks for an improvement in the performance of these electronic devices. Moreover, a problem of signal delay in electrical wiring arises. Furthermore, a provision for EMI/EMC (Electro-Magnetic Interference/Electro-Magnetic Compatibility) is indispensable for achieving the increase in the transmission rate of the electric signal and the increase in the density of the signal wiring. Attention is paid to an optical interconnection (optical wiring) as means for eliminating the bottlenecks in these wirings.
This optical interconnection is considered to be applicable to various situations such as the interconnection between devices, between in-device boards or between in-board chips. An optical transmission communication system, in which an optical waveguide formed on a substrate is used as a transmission line, is considered to be suitable for a transmission over relatively short distances such as the distance between the chips, for example. For the optical transmission communication system using such an optical waveguide, an important problem is to establish a process of making the optical waveguide.
Requirements for such an optical waveguide are a low optical loss and easiness in making. Optical waveguides for satisfying these requirements include a low-loss optical waveguide using a quartz base material, for example. As has been proved by an optical fiber, quartz is excellent in light transmittance. Thus, the loss can be reduced to 0.1 dB/cm or less when the optical waveguide is made of quartz. However, the use of quartz has problems such as a long time required to make the optical waveguide, a high temperature (800xc2x0 C. or higher) at the time of the making, a difficulty in increasing an area and a high cost. It is considered that a high polymeric material such as polymethyl methacrylate (PMMA) or polyimide is used as the material for solving these problems and making it possible to make the optical waveguide by a low-temperature process.
Taking into consideration the increase in the density of an optical transmission using the optical waveguide, it is desirable t hat an optical signal is bidirectionally propagated through the optical waveguide. However, the system for intending the optical signal to bidirectionally propagate has various problems to be solved, such as the form of an entry of the light from a light emitting device into the optical waveguide, the form of an exit of the light from the optical waveguide to a photodetector, an arrangement of the light emitting device and the photodetector with respect to the optical waveguide, or crosstalk between the signals bidirectionally propagated.
The invention is designed to overcome the foregoing problems. It is an object of the invention to provide an optical waveguide device and an optical transmitting and receiving device which enable bidirectional communication by allowing the optical signal to bidirectionally propagate by using the optical waveguide formed on the substrate and used as the optical wiring, a method of manufacturing an optical waveguide device and a method of manufacturing an optical transmitting and receiving device.
An optical waveguide device of the invention comprises an optical waveguide formed on a substrate and enabling a light to bidirectionally propagate therethrough; and a trench-shaped space formed in the optical waveguide near at least one end of the optical waveguide so as to cross a direction of light propagation, the trench-shaped space being capable of switching the light propagating through the optical waveguide. The optical waveguide can comprise a high polymeric material. Moreover, the substrate can comprise an inorganic material containing at least one of silicon, quartz, glass and ceramics or an organic material.
An optical transmitting and receiving device of the invention comprises an optical waveguide formed on a substrate and enabling a light to bidirectionally propagate therethrough; a trench-shaped space formed in the optical waveguide near at least one end of the optical waveguide so as to cross the direction of light propagation, the trench-shaped space being capable of switching the light propagating through the optical waveguide; a photodetector for receiving a coming light switched by the trench-shaped space; and a light emitting device for emitting a transmitting light toward the trench-shaped space.
In the optical waveguide device or the optical transmitting and receiving device of the invention, the optical waveguide can include a core which the light propagates through; and a cladding formed so as to surround the core. In this case, it is desirable that the trench-shaped space is formed so as to cross at least the core.
Moreover, in the optical waveguide device or the optical transmitting and receiving device of the invention, the trench-shaped space can have a first boundary surface capable of internally reflecting a coming light propagating through the optical waveguide, thereby guiding the coming light out of the optical waveguide; and a second boundary surface capable of passing therethrough a transmitting light traveling in the direction opposite to the direction of propagation of the coming light, thereby guiding the transmitting light into the optical waveguide. Preferably, when n denotes a refractive index of a material constituting a principal part of the optical waveguide, an angle xcex81(xc2x0) of the first boundary surface to the direction of light propagation satisfies xcex81 less than 90-sinxe2x88x921(1/n), and an angle xcex82(xc2x0) of the second boundary surface to the direction of light propagation satisfies xcex82 greater than 90-sinxe2x88x921(1/n).
Moreover, in the optical waveguide device or the optical transmitting and receiving device of the invention, at least one end of the optical waveguide can form an end surface which is substantially perpendicular to the direction of light propagation and which is capable of passing therethrough the externally incoming transmitting light in substantially the same direction as the incoming direction, and the transmitting light entering through the end surface passes the second boundary surface, the trench-shaped space and the first boundary surface in sequence so that the transmitting light is guided into the optical waveguide.
Moreover, in the optical waveguide device or the optical transmitting and receiving device of the invention, at least one end of the optical waveguide may form an end surface which forms a predetermined angle with the direction of light propagation so as to cross the direction of light propagation and which is capable of internally reflecting the transmitting light entering through an upper surface or a side surface of the optical waveguide, and the transmitting light reflected by the end surface passes the second boundary surface, the trench-shaped space and the first boundary surface in sequence so that the transmitting light is guided into the optical waveguide. In this case, preferably, when n denotes the refractive index of the material constituting the principal part of the optical waveguide, an angle xcex83(xc2x0) of the end surface to the direction of light propagation satisfies xcex83 greater than sinxe2x88x921(1/n).
A method of manufacturing an optical waveguide device of the invention comprises the steps of forming on a substrate an optical waveguide enabling a light to bidirectionally propagate therethrough; and forming a trench-shaped space in the optical waveguide near at least one end of the optical waveguide so as to cross the direction of light propagation, the trench-shaped space having a first boundary surface and a second boundary surface, the first boundary surface being capable of internally reflecting a coming light propagating through the optical waveguide and thereby guiding outward the coming light through the upper surface or the side surface of the optical waveguide, the second boundary surface being capable of passing therethrough a transmitting light traveling in the direction opposite to the direction of propagation of the coming light and thereby guiding the transmitting light into the optical waveguide through the first boundary surface.
A method of manufacturing an optical transmitting and receiving device of the invention comprises the steps of forming on a substrate an optical waveguide enabling a light to bidirectionally propagate therethrough; forming a trench-shaped space in the optical waveguide near at least one end of the optical waveguide so as to cross the direction of light propagation, the trench-shaped space having a first boundary surface and a second boundary surface, the first boundary surface being capable of internally reflecting a coming light propagating through the optical waveguide and thereby guiding outward the coming light through the upper surface or the side surface of the optical waveguide, the second boundary surface being capable of passing therethrough a transmitting light traveling in the direction opposite to the direction of propagation of the coming light and thereby guiding the transmitting light to the optical waveguide through the first boundary surface; forming a photodetector for receiving the coming light reflected by the first boundary surface, on the upper surface or the side surface of the optical waveguide near the first boundary surface; and forming near the end surface a light emitting device for emitting the transmitting light toward the end surface.
In the optical waveguide device of the invention, the light propagating through the optical waveguide is switched by the trench-shaped space which is formed in the optical waveguide near at least one end of the optical waveguide formed on the substrate so as to cross the direction of light propagation. Herein, the phrase xe2x80x9cthe light is switchedxe2x80x9dmeans that the light propagating through the optical waveguide is guided to routes differing in accordance with the direction of propagation of the light.
In the optical transmitting and receiving device of the invention, the light propagating through the optical waveguide is switched by the trench-shaped space which is formed in the optical waveguide near at least one end of the optical waveguide formed on the substrate so as to cross the direction of light propagation. The coming light switched by the trench-shaped space is received by the photodetector, while the transmitting light is emitted from the light emitting device toward the trench-shaped space.
Other and further objects, features and advantages of the invention will appear more fully from the following description.